Page 283 - ICSE Math 6

Mental Maths
(b) 1. (a) True (b) True (c) False (d) True (e) True
0 1 2 3 4 5 6 7 8 9 10
Thus, 3 + 4 = 7 2. (a) a; multiplicative identity (b) commutative
(c) divisor (d) closure; whole (e) distributive; 2
(c) (f) zero
0 1 2 3 4 5 6 7 8 9 10
Thus, 7 + 2 = 9 Practice Time
1. 1,02,998 2. 76,85,950

6. (a)
0 1 2 3 4 5 6 7 8 9 10 3.
Thus, 8 –5 = 3 0 1 2 3 4 5 6 7 8 9 10 11
Thus, 2 + 7 = 9

(b) 4.
0 1 2 3 4 5 6 7 8 0 3 6 9 12 15 18 21
Thus, 6 –3 = 3 Thus, 3 × 6 = 18
5. 25,600 6. 1,73,800 7. 4
8. 10,032 9. (a) 5,050 (b) 840
(c) 10. ` 3,100 11. 170 shirts; ` 1,19,000
0 1 2 3 4 5 6 7 8
Thus, 7 – 7 = 0 Think Smart
1. 2 2. 9
7. (a)
0 4 8 12 3.
Thus, 4 × 2 = 8 0 1 2 3 4 5 6 7 8 9 10
Thus, 3 + 6 = 9
(b) 4. 30; 42
0 3 6 9 12 15 18
Thus, 3 × 5 = 15 Chapter 3
Exercise 3.1
(c) 1. (a) Expenditure of ` 5,000
0 7 14 21 28
Thus, 7 × 3 = 21 (b) 250 km west of Delhi
8. (a) 378; 387 > 378 (b) 1,001; 1,001 < 1,101 (c) Early by 25 minutes
(c) 3,456; 3,456 < 6,543 (d) 36,789; 36,789 < 3,67,899 (d) 200 m below sea level
(e) Increase of 10
Exercise 2.2 (f) 20°C above freezing point
1. (a) 456 (b) 124 (c) 8,769 2. (a) +` 26,500 (b) +` 3,000 (c) –` 5,000
2. (a) 1,700 (b) 500 (c) 16,000 (d) 500 (d) +100 m (e) –3,000 m (f) –10 m
3. (a) 24,514 (b) 15,246 (c) 4,257 (d) 1,38,414 3. (a)
4. (a) 3,50,000 (b) 60,000 (c) 45,100 (d) 50,00,000 –3 –2 –1 0 1 2 3 4 5
5. (a) 24,850 (b) 4,27,900 (c) 8,12,600 (d) 16,84,000 (b)
–1 0 1 2 3 4 5 6 7
6. 13 6750 519
– 65 (c) –5 –4 –3 –2 –1 0 1 2 3
25
–13 Quotient × Divisor + Remainder (d)
120 = 519 × 13 + 3 –8 –7 –6 –5 –4 –3 –2 –1 0
–117 = 6,750 = Dividend
3 4. (a) –26 is to the left of –13.
7. (a) 5 (b) 0 (c) Not defined (d) 5 (b) –9 is to the left of 18.
8. 29,970 9. 24 10. 765 (c) –29 is to the left of –13.
(d) –100 is to the left of –67.
Exercise 2.3 5. –8, –7 and –6 6. –13, –14 and –15
1. (a) 11,110; 1,11,110 (b) 4,44,444; 5,55,555 7. (a) –4 > –5 > –6 > –7 > –8 > –9
2. (a) 781; 3,906 (b) 15; 21
(b) –7 > –8 > –9 > –10 > –11 > –12

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